The alternation response in rats. -I

The effects of inter-trial interval, work and hunger drive

Abstract

Three experiments were undertaken to determine the effect of inter-trial interval, work and hunger drive on the alternation response of white rats.
Exp. I. A simple T-maze was used. After exploration and pretraining, 30 white rats were divided into 5 groups. Inter-trial intervals differed from 0, 10, 20, 30 to 60 seconds in each group. All rats were given two blocks of 11 successive free choice trials per day for 5 days following approximately 24 hrs. of food deprivation. A 5 min. rest period was introduced between the two blocks of trials. The following two days constituted an extinction period.
Results : It was found that : 1) The percent alternation during the experimental period decreased as the inter-trial interval increased. The scores of groups IV and V were lower than chance. Following the 5 min. rest period, alternation was higher than during the 60 sec. interval, and after 24 hrs. it returned to the chance score.
2) The percent alternation during extinction in all groups was higher than chance.
3) The higher the alternation, the longer the running time.
Exp. II. Three types of T-maze were used. Type A was the same as used in Exp. I. The arms of type B were 125cm. longer than A. In type C, the arms used in type B were inclined 6 degree from the choice point to the goal boxes.
Thirty white rats were divided into 5 groups which differed in amounts of work and inter-trial intervals (see Table 2). The rest of the procedure was the same as in Exp. I.
Results : It was found that : 1) Increased work resulted in indreased alternation in the same intervals.
2) The alternation increments due to increasing work were constant whether the interval was 20 or 60 seconds.
3) The alternation increments due to decreasing interval were constant whether work was A or C.
4) All groups showed above chance alternation during extinction.
Exp. III. Eighteen rats were divided into three groups. The hours of food deprivation were 12, 24 and 48 respectively. The interval was 20 seconds.
Results : It was found that : 1) The percent alternation decreased as the hunger drive increased. The score of the 48 hrs. group was lower than chance.
2) A parallel relationship was found between alternation and running time.
3) The extinction scores of all groups were higher than chance.
Conclusions : The results indicate that alternation. depends upon the three factors studied. In some cases, the percent alternation decreased below chance. Because these findings have shown that repetitive responses occured above chance, some facilitatory effect must be considered as an explanation of the phenomena. Previous authors have asumed only an inhibitory factor in explaining alternation responses.
The results of three experiments showing higher alternation during extinction and the results of Exp. III suggest a facilitatory effect closely related to reinforcement, although the animals were permitted to take food whether they chosed the right or the left turn.
The fact that a shorter interval and a greater amount of work resulted in higher alternation would indicate that an inhibitory effect produced by the response might be the cause of alternation. The parallel relationship between alternation and running time also comfirms a response-produced inhibition hypothesis.
From the above considerations, it was felt that alternation responses result from the opposing processes of facilitation and inhibition which waxed and waned in different manners and at different speeds.